An implantable cardiac stimulus device (ICSD) typically senses cardiac electrical signals in an implantee and uses the sensed signals to classify the implantee's cardiac rhythm as normal/benign or treatable/malignant. Illustrative treatable arrhythmias may include ventricular fibrillation and/or ventricular tachyarrhythmia. Other rhythms may also be considered “treatable” depending upon patient characteristics and physician preferences.
If a treatable arrhythmia is identified and defibrillation or cardioversion is to be delivered, an ICSD typically needs some period of time to prepare for therapy delivery. For example, a three, six or nine-volt battery supply may be used to provide hundreds or even thousands of volts of stimulus amplitude by charging a capacitor for several seconds using a charging circuit. As a result, once a treatable condition is identified, there is a charging time period corresponding to the preparations of the device to deliver therapy. Anti-tachycardia pacing (ATP) may not require such a charging delay, however, to ensure that therapy is appropriate, a system delivering ATP may include a delay for confirmation of arrhythmia before therapy delivery.
Some treatable arrhythmias may be intermittent or may spontaneously revert to a benign rhythm. If an apparently treatable arrhythmia spontaneously reverts to a benign rhythm, therapy becomes unnecessary. In general, therapy delivery should be managed to avoid unnecessary therapies.
To avoid unnecessary therapy, devices may perform rhythm confirmation just before delivering therapy. New or alternative methods for managing delivery through therapy confirmation are desired.